Common Stock - Summary of Information and Changes in Stock Options with Regard to Stock Option Plans (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of shares under stock option, Beginning of the year	11,535,566	10,274,477	11,367,995
Number of Shares Granted	3,389,547	3,072,086	2,428,406
Number of Shares Spin-off	(1,567,348)
Number of Shares Cancelled	(498,967)	(329,002)	(247,426)
Number of Shares Exercised	(1,977,665)	(1,481,995)	(3,274,498)
Number of shares under stock option, End of the year	10,881,133	11,535,566	10,274,477
Number of stock options, Vested or expected to vest	10,739,679
Number of stock options, Exercisable	5,903,712	6,324,117	5,231,150
Weighted Average Exercise Price, Beginning of year	$ 58.36	$ 54.11	$ 43.52
Weighted Average Exercise Price, Stock Options Granted	$ 69.00	$ 63.96	$ 77.99
Weighted Average Exercise Price, Stock Options Spin-off	0
Weighted Average Exercise Price, Stock Options Cancelled	$ 70.32	$ 66.78	$ 55.58
Weighted Average Exercise Price, Stock Options Exercised	$ 53.56	$ 38.75	$ 34.59
Weighted Average Exercise Price, End of the year	$ 61.22	$ 58.36	$ 54.11
Weighted Average Exercise Price, Stock options vested or expected to vest	$ 61.22
Weighted Average Exercise Price, Stock Options, Exercisable	$ 55.06	$ 49.29	$ 40.56
Weighted Remaining Contractual Term, Outstanding	6 years 8 months 19 days	5 years 4 months 13 days
Weighted Remaining Contractual Term, Vested	6 years 8 months 19 days
Weighted Remaining Contractual Term, Exercisable	5 years 1 month 24 days
Stock Options Aggregate Intrinsic Value, Beginning	$ 155,892,094
Stock Options Aggregate Intrinsic Value, Ending	87,998,114	155,892,094
Stock Options Average Aggregate Intrinsic Value, Vested or expected to Vest	86,854,138
Stock Options Average Aggregate Intrinsic Value, Exercisable	$ 85,503,217

Share based compensation arrangement by share based payment award options spin off in period.

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The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Net number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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